Dieect current timing device



D. R. PRICE DIRECT CIERRENT TIMING DEVICE Filed May 6, 1951 June 13,1933. 1,9i4,2.15

Inventor David R. Price by max His Attorney.

Patented June 13, 1933 UNITED STATES PATENT OFFICE DAVID R. PRICE, OFSWAMPSCOTT, MASSACHUSETTS, ASSIGNOR TO GENERAL ELECTRIC I COMPANY, ACORPORATION OF NEW YORK manor ommnnr rmme nnvrcn Application filed Kay6,

My invention relates to an electric timing device suitable for operationfrom a direct current source of supply. 1

The now well known synchronous motor driven timing device operated froman alter hating current circuit of regulated frequency has certainadvantages over spring driven timing device and a timing device havingcorresponding advantages is needed where.

of the condenser discharge circuits are maintained fixed so that thetime necessary for the condenser to discharge from the maximum voltageto the minimum voltage is fixed and constant. The charging period of thecondenser may vary slightly if the voltage of the source of supplyvaries. However, I make the charging period very much shorter than thedischarge period so that the possibility of error on account ofvariations in the,sup-' ply voltage is minimized. The. control of thecondenser charging circuit is preferably accomplished by anelectromagnet and the energizing coil of this electromagnet is includedin the condenser discharge circuit so that the operation of theelectromagnet is responsive to the maximum and minimum voltages of thecondenser. The armature of this electromagnet which is employed to openand close the condenser charging circuit is also employed to actuateeither directly or indirectly any form of timing'device.

The features of my invention which are believed to be novel andpatentable will be inted out in the. claims ap ended hereto. or a betterunderstanding 0 my invention, reference is made in the followingdescription to the accompanying drawing which represents in Fig. 1 apreferred embodiment of my. invention as employed to operate a contactmaking clock, and Fig. 2 shows a volta e time curve of a condenser whichwill be re erred to in explaining the operation of the invention.

Referrin to Fig. 1 in the drawing, I have represente my invention asdirectly applied to the operation of a contact making clock. It might beused for any other timing purse, such as to drive a chart of a recordinginstrument or for operating the timing element of a demand meter eitherdirectly as represented or through relay devices. As represented theclock indicated at 10 and. the contact cam 11 are driven throu h wormgears 12 and 13 from ratchet whee 14.

The ratchet wheel is operated by an electromagnet or ratcheting relaycomprising the magnetic core 15, energizing winding 16, armature 17 andpawl 18. A stop pawl 19 may be added to prevent any appreciable backwardmovement'of the ratchet wheel 14. The armature 17 isrepresented in itsdetracted position to which it is biased by its resilient spring pivot20. The mechanical features thus far mentioned are old and may be variedto suit different operating requirements.

The arrangement for energizing coil 16 from a direct current source ofsupply so that the armature will be actuated at a uniform rate isbelieved to be novel. The direct current source is indicated at 21. Oneside of this source is connected to coil 16v through armature spring 20,the magnetic armature 17, a pair of contacts 22 and 23 and a resistance24. The other side of the source is connected to the other side of thecoil through closed and discharged through resistance 24' and coil 16when the above-mentioned contacts areopen. The contact 23, theresistancesand the condenser are shown adjustable. They may be adjustedto obtain the desired relay actuating interval, but when prodperlyadjusted for this purpose they or narily do not need further adjustmentunless the time interval is tobe changed. To give a practical examplebut not to limit the invention, it may be assumed that coil 16 contains20,000 or more turns of fine wire, such as .003 inch enameled wire.Resistor 24 may have approximately 20,000 ohm resistance and 26 about5,000 ohm resistance. The condenser 27 may have from one to fivemicrofarads capacity. Such a combination may be used to reciprocate thearmature 17 from about two complete operations a second to about one infive seconds depending upon the adjustment. I

The operation of the device is as follows: In the position shown thearmature 17 is in its detracted position and closes the charging circuitof the condenser to the source of sup ply. During this period a chargingcurrent flows to the condenser and the voltage across it graduallyincreases. Resistance 26 prevents an instantaneous charging of thecondenser but allows the charge to build up gradually. The voltage ofthe condenser is also applied across resistance 24 and coil 16 so thatwhen this voltage reaches the proper predetermined maximum value theelectromagnet is energized sutliciently to attract armature 17 therebyopening the condenser charging.

circuit at contact 22. The condenser now'discharges through coil 16. Thecurrent through coil 16 decreases as the condenser charge leaks oiluntil a condition is reached where the magnetism of core 15 can no lon rhold the armature 17 in the attracted position and the latter moves awayunder the action of spring 20 and closes the condenser charging circuitagain. Owing to the materially diil'erent resistance relations in thecharging and'discharging circuits of the condenser the charging periodis relatively short as compared to the dischar period.

Fig. 2 represents e relations mentioned above and shows the condenservolta variation with respect to time. Curve A represents the variationof condenser voltage with respect to time during an initial chargingperiod, A representing zero voltage and B the maximum condenser-volts ewhich is that value sufiicient to actuate. t e electromagnet .and openthe charging circuit. Curve BC represents the condenser volta withrespect to time during a discharge perlod, C being the voltage where thecurrent through coil 16 has decreased to a value where armature 17 isreleased. The values'B and C are also proportional to the current whichflows through coil 16. At point C some charge remains on the condenserso that the subsequent chargin periods are represented by onl portion 0%ofthe initial charging curve. The charg ing time is thereforerepresented by the distance X and the discharge time by the distance Yand a complete timing cycle by the distance X plus Y.

initial pull.

It will be evidentthat the values B and C are independent of variationsin the-supply of voltage at. 21. The time Y is also independent of suchvariations. The only time value that can change is the charging period Xwhich is such a small portion of the total time involved in a completecycle that it may be neglected in most cases where the supply of voltageis fairly constant. The time error incident to high and low voltageconditions will tend to cancel out in any event if the apparatus iscalibrated for an average voltage condition.

In many cases timing devices are used for operating time switches, theresetting apparatus of demand meters and for other purposes where masterclock accuracy is not required and my invention issuitable for suchpurposes even where the direct current source of supply varies somewhat.

It will not do to eliminate resistance 26 entirely except where aconstant source of supply is available. Some means such as resistance 26or its equivalent is desirable to prevent instantaneous charging of thecondenser when the chargingc ircuit is closed. The condenser should becharged at a sulficiently slow rate to enable the electromagnet tocorrectly select the predetermined voltage B at which charging is stoped. If the condenser were allowed to charge instantaneously the value Bwould rise and fall in proportion to variation in the supply voltage andthe discharge time Y would no longer be constant. 3

The resistance characteristics of the circuits will preferably be madeindependent of temperature variations and resistance elements having theproper temperature coeflicient of resistance to eliminate temperatureerrors should be used. Where the armature 17 is used in combination witha pawl 18 as represented todirectly actuate a ratchet wheel. it will bedesirable to arrange matters so that the armature will be attracted atthe same value of flux in core 15 for all conditions of loading. Thearmature pawl 18 should preferably have the load removed therefrom atthe instant of attraction. This may be accomplished by making itsreciprocating movement slightly greater than the distance between theteeth in the ratchet wheel 14 so that no load is applied until thearmature has moved towards the magnet 15 slightly and is thus subject toastronger pull than its The faces of the magnet 15 against which thearmature rests when in the attracted position are preferably of nonmaetic material so that there will be no ten ency for the armature tostick and will by Letters Patent of the United States, is,-

1. A timing device 'comprisin energy stora e means, means for aternately charging sai energy storage means to a predetermined maximumvoltage in a relatively short interval of time and discharging saidenergy storage means to a predetermined minimum voltage in apredetermined longer interval of time and time means operated inresponse to said predetermined maximum and minimum voltages, said timingdevice as a whole having a timing function de ndent upon the length ofthe charging and discharging time intervals.

2. A timing device comprising a condenser,

- a direct current circuit for charging said positions respectively inresponse to termined relatively high and low 'vo condenser, anelectromagnet having an energizing circuit connected across thecondenserand comprising a discharge circuit therefor, and an armature for theelectromagnet movable to attracted and. detrargaed el tages across thecondenser, said armature servingto open and close the condenser chargincircuit in its attracted and detracted positions respectively, thecharging and discharging circuits of the condenser having constants suchthat the charging and discharging riods of the condenser are of appreciale duration and the discharging period is appreciably longer than thecharging period, said periods determining the timing function of thedevice.

- 3. A timing device comprising a condenser, asfdirect current circuitfor. charging said condenser, an electromagnet having an energizingcircuit connected across said condenser and a movable armature foropening the char 'ng circuit in response to a predetermin voltage acrossthe condenser and closing the charging circuit in to a predeterminedlowervoltage acres the condenser, the charging circuit of the condenserincluding resistance means for preventing the condenser from beingcharged mstan -ly when the circuit is closed, and the electromagnetenergizing circuit containing "ance m ns omakingflthecondenaar'diacharge period apprecia y longer resistg z r KcAtimingdevicecom r'ming'a a chi w indirect current source of SHPP Y formid m magnet'havlng an ai hatI claim as new and desire tosecureelectric.

nected across the condenser, a movable armature for said electromagnetfor .altemately opening and closing the charging response topredetermined maximum and voltages across the condenser respectively andmeans'for limiting the chargrate 0 said condenser so that it is chargedsu ciently slowly that its maximum ch is determined b the openingof thechar circuit by the ectromagnet and is inde'pen ent of the supsly vol a..tin,

5. A immg evicecomfprisin' acondenser,

a charging circuit there or, a net current source of sup ly forfleaidcircuit, an electroma et for ternately opening and closing sai chargingcircuit m use to predetermined maximum and minimum d of energization ofthe electromagnet, a,d1scharge circuit for said condenser including theenerlgizing winding of said electroma et w ereby the chxging circuit isopen in response to a p etermined voltage across the condenser andclosed at a predetermined lower voltage across the condenser, theconstants of the charging circuit being such that the maximum charge onthe do denser is determined by the operation 0 the electromagnet and isindependent of the vol 7 the source of supply so 10 as such v0 ta issuflicient for t e purpose ascribed, and t e constants of. the dischargelonger than the charging {P611013 6. A timing device com rising acondenser, a direct current chargin circuit and a discharge circuittherefor, an electronic et having an armature movable to attrac anddetracted :tions for respectively ope and-closing the condenser chacircuit and having an energizing coil included in the discharge circuitfor the condenser the ar-' rangement being such that the con enser 'isalternately charged throu the circuit closed by the armature and discarged through the energizing coil when the charging circuit is opened,the charging and discharging circuits having constants such that thecharging period is "of sufiicient duration that the maximum condensercharge is determined by the o ning of the charging circuit and thedisarge period is of agpreciablylonger duration, and a timing eviceoperated by the movement ofsaid armature.

circuit being such as to make the discharge "period materially Inwitness whereof, I have hereunto set 7 my hand.

